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[Bug rtl-optimization/58295] [4.8/4.9 regression] Missed zero-extension elimination in the combiner
- From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 06 Sep 2013 13:18:13 +0000
- Subject: [Bug rtl-optimization/58295] [4.8/4.9 regression] Missed zero-extension elimination in the combiner
- Auto-submitted: auto-generated
- References: <bug-58295-4 at http dot gcc dot gnu dot org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58295
--- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Therefore, we can conclude that the original case tried by the combiner is
> the best way to merge/reduce the redundant zero extension insn.
Yes and, although x86 is the dominant architecture, it shouldn't be allowed to
penalize all the others. I think we should restrict the effect of r191928, in
particular it makes little sense as-is if you also define PROMOTE_MODE as on
most RISC architectures.